In a semiconductor fabrication process using an exposure device, alignment with an alignment mark formed in a previous process is performed and a pattern for the next layer is exposed thereon. Then, superposition deviations between the exposed pattern and a substrate are measured from an image capturing a superposition measuring mark formed in the previous process and a superposition measuring mark of the exposed pattern simultaneously. Visible light or light in a long wavelength region is generally used for alignment and superposition measurement. Various patterns are used as the alignment mark or the superposition measuring mark and representative examples include the box in box type, bar in bar type, and line and space type. When designing these marks, the mark dimensions, densities, coverage, convex marks, concave marks, and segment marks are adjusted and selected so that a sufficient margin can be left for exposure conditions (exposure value, focus) for a device pattern.
In recent years, however, with increasingly finer patterns of semiconductor devices, technologies such as the sidewall manufacturing process technology to form a pattern in dimensions less than the resolution limit of a exposure light have been adopted. In the sidewall manufacturing process, a hard mask is formed by forming a sidewall pattern less than the resolution limit on the sidewall of a film pattern to be a core and removing the core. Thus, if a mark pattern is formed by the above method, only a sidewall pattern in an edging shape surrounding a core is obtained in the end because even if a film pattern of the core having a mark shape is formed in dimensions equal to the resolution limit or more, the film pattern of the core is removed thereafter. Moreover, such a sidewall pattern in the edging shape has dimensions less than the resolution limit of a measuring light, posing a problem of measuring difficulty by an optical microscope using the a measuring light.